Problem: A supplier for the military needed a way to more efficiently create and mold a proprietary mix of thermoplastics to form sacrificial tooling for aerospace parts.
Solution: KraussMaffei’s DCIM technology compounds and molds materials in one process.
By Karen Hanna
In service of a military branch known for its “Aim high” slogan, one composite parts maker is taking its small-scale injection molding operation to the next level. It’s hoping a KraussMaffei (KM) machine that can perform both compounding and molding can help it elevate its game.
At a display in KraussMaffei’s booth at NPE, Brennen Shelton, GM of Fiber Dynamics Inc. in Wichita, Kan., showed off parts that demonstrate the challenges his company regularly confronts. He turned over in his hand one segment of a wind-tunnel propeller designed to handle 1,500 Gs of force. While the part featured numerous hollow sections, its fit in Shelton’s hand belied its complexity — it had been cut in pieces for easier transport, after being manufactured in one piece to exacting standards from highly engineered thermosets. When produced as designed, it weighs in at 95 pounds.
The process for manufacturing such parts can be cumbersome, with multiple steps that include machining, compounding and casting.
Typically, Fiber Dynamics has started with billets made from a proprietary mix of thermoplastics, fillers and additives, which it then machines into hollow forms that become the mandrels for its parts. It covers those mandrels with a thermoset composite material and melts away the thermoplastics in the final step of the process, known as the Lost Core Tooling System (LCTS), leaving behind the final aerospace parts.
Unfortunately, the process gives Fiber Dynamics limited control over the materials it uses, and machining is labor-intensive and tricky.
With a new project for the U.S. Air Force looming, Shelton and other company officials began looking for a more efficient process.
“We knew that injection molding was the right process for that," said Darrin Teeter, the owner of Fiber Dynamics. “But we have been unsuccessful with conventional screw-type injection molding systems with a couple other vendors that we’ve tried in the past. We’ve been unsuccessful in getting the materials to work due to their unique characteristics.”
Scoping out the possibilities
Teeter founded Fiber Dynamics 40 years ago, and the company employs around 100 people, mainly focused on resin-transfer molding.
For the Air Force project, he wanted to find a way to avoid the machining processes his company normally performs, and to provide more control over the material mixes it uses.
As a former research associate of the National Institute for Aviation Research (NIAR) at Wichita State University, which he described as the “Disney World of composites manufacturing,” he knew just where to turn.
Over about the past year, NIAR’s Advanced Technologies Lab for Aerospace Systems (ATLAS) has operated a GX 450-1400 Direct Compounding Injection Molding (DCIM) machine from KraussMaffei. It not only can mold the sacrificial tooling Fiber Dynamics needs, at the touch of a button, it can compound the materials used in the tooling — a two-in-one process that offers a bevy of potential benefits.
“When we discovered the potential to produce our LCTS materials by thermoplastic injection molding, we were able to use the laboratory machine at ATLAS to carry out important validation processes. The results were excellent, so we quickly decided to purchase the DCIM system,” Teeter said.
The rest went “amazingly quick,” he said, following a trip to KraussMaffei’s headquarters in Parsdorf, Germany, just outside Munich.
“Took a trip to Munich and somehow I had no intentions or even thought of buying a machine, but somehow that happened,” he said.
Improved control, efficiency
At NPE, Shelton and Teeter pointed out features of the new 1,200-plus-ton GX 1100-4300 DCIM KraussMaffei showed at its booth, along with displays from NIAR. The same model of machine was due at Fiber Dynamics’ plant in mid-May, as part of what the company was touting on its website as an “exclusive technology triad” with NIAR and KraussMaffei. Representatives of KraussMaffei and Fiber Dynamics, including Teeter, said they expect the DCIM process to provide numerous advantages, with less need for machining, the freedom to produce a wider variety of materials and quicker production.
Eugen Schubert, sales and application manager for KraussMaffei, describes himself as the
“the bridge or interface” who has brought the DCIM technology to Fiber Dynamics. After working a dozen years for KraussMaffei in Germany, he’s now based in Wichita.
The technology is one way for users to spread their wings.
“It’s not just injection molding, it’s a combination of injection molding machinery with extrusion,” Schubert said.
“The compounding, casting and machining processes are eliminated, saving days of process time,” Teeter said.
According to KraussMaffei, a single-screw extruder handles material preparation, and it can provide material savings of up to 50 percent. DCIM machines are particularly cost-effective for smaller components with shot weights between about 0.1 pound to 4.4 pounds.
Fiber Dynamics’ parts are often much larger, but the DCIM is appropriate for them, too.
“With the DCIM machine, we have the option to continuously extrude material into the mold and then ‘pack it out’ with the final injection molding shot,” Teeter said.
He and Schubert said they expect the DCIM process to give Fiber Dynamics more freedom in producing materials for the thermoplastic tooling. With dosing equipment right at the machine, the DCIM can homogenize materials and then inject them — with minimal thermal exposure.
“There is no ready-to-use material formulation which you can get in form of pellets, which is usually used in injection molding ... ” Schubert said. “Depending on the needs of the lost core or the end product, they can on-the-fly or between some different molds, they can change the formulation. They don't need to batch or plasticize it again.”
The ability to produce more materials is an advantage Teeter cited, too.
“The ability to test a variety of different formulations and quickly develop new ones is crucial to the success of our program,” he said. “Externally compounded formulations are generally not practical for our work and jeopardize the proprietary nature of our solutions.”
With the DCIM, Fiber Dynamics will be able to mold its tooling, melt the tooling and reuse the materials multiple times — a luxury that’s not as achievable with its earlier process, which has subjected materials to longer thermal exposures.
The current process takes about two weeks, or even more, with long cycle times and a great deal of labor required at various stages, Shelton said.
While Teeter said in early May he was not sure about cooling times for the parts his plant will be producing on the DCIM, he predicted the entire production time will be just one-eighth as long — or even faster.
In trials in Munich, Shelton said, “We were outputting a three-and-a-half-pound structure and what was it? About 60-90 seconds.”
“We can get a net shape of the injection tooling. The other process requires machining and so on,” Schubert said. “There are also various processes we are cutting down to one process.”
According to KraussMaffei, compared to the earlier process, the DCIM machine also requires less energy and leaves a smaller carbon dioxide footprint.
Fiber Dynamics’ website boasts: “This cutting-edge technology paves the way for your company to achieve low-cost, high-rate production of complex composite structures.”
“It’s going to make our processes all-around better,” Shelton said.
Sky’s the limit
While he plans to use the new GX 1100-4300 to build parts for the Air Force, Teeter is setting his sights higher — that project doesn’t account for the machine’s full capacity.
“Since we do not foresee using the full capacity of the machine, we also have the ability to look at or to do other engineered thermoplastics, like PEEK [polyetheretherketone] and fiber-filled [materials]. ... With some adaptation, we could also do the overmolding with the continuous-fiber-reinforced materials,” he said.
In addition to its work for the military, Fiber Dynamics also makes parts for the automotive and sporting goods markets.
The GX 1100-4300 could come in handy for that work, too, but its initial project demonstrates how much confidence Fiber Dynamics has in its capabilities to do sophisticated work well as part of the overall project for the Air Force.
The aerospace parts are “a very high-temperature application,” Teeter said.
“You’ve got like a 400,000-horsepower motor driving 97 blades [in a] 30-foot-diameter tunnel ... very, very complex parts, high requirements. ... It’s really critical for us and for the national defense program, as well,” he said.
Contact:
KraussMaffei Corp., Florence, Ky., 859-283-0200, www.kraussmaffei.com
